# Produce CuCl2 from CuSO4

I have a large amount of copper sulfate available and I am interested in obtaining copper chloride from it. What is the easiest way to do so?

I have considered mixing an aqueous solution of copper sulfate with sodium chloride, but I think that it would be difficult to separate the resulting sodium sulfate from the copper chloride. My other idea is to first react the copper sulfate with sodium carbonate and then react the resulting copper carbonate with hydrochloric acid, which would produce copper chloride (the other products would be $\ce{CO2}$ gas and water). I am trying to find a cost effective method for performing this reaction.

## 5 Answers

You cannot obtain $\ce{CuCl2}$ mixing $\ce{CuSO4}$ and $\ce{NaCl}$ because both are very soluble, the second strategy seems good because $\ce{CuCO3}$ is insoluble in water, and you can react the new salt with $\ce{HCl}$.

Good luck.

Here's a much more direct method: just add a stoichiometric amount of calcium chloride to a concentrated aqueous solution of copper sulfate:

$$\ce{CuSO4(aq) + CaCl2(aq) -> CaSO4(s) + CuCl2(aq)}$$

If the copper sulfate you have is in the anhydrous form (white powder), then add 695.3 mg of pure $\ce{CaCl2}$ per 1000 mg of pure $\ce{CuSO4}$. If your copper sulfate is in the form of the pentahydrate ($\ce{CuSO4.5H2O}$, striking blue crystals), then add 444.5 mg of pure $\ce{CaCl2}$ per 1000 mg of pure $\ce{CuSO4.5H2O}$.

The low solubility of calcium sulfate (~0.2 g per 100 g of water at 20°C) is what drives the reaction forwards. This double displacement reaction does not happen if you use sodium chloride, because sodium sulfate is highly soluble. Simply filter the solid out and obtain a relatively pure solution of copper(II) chloride, with small amounts of calcium and sulfate contamination. Drying the solution completely will net $\ce{CuCl2}$ crystals.

Try adding pure salt to aqueous CuSO4 and freeze out Glauber's salt (Na2SO4.10H2O):

2 NaCl + CuSO4 (aq) --Freeze--> Na2SO4.10H2O + CuCl2 (aq)

This path avoids the formation of problematic CaSO4 to quote a source (http://homepages.see.leeds.ac.uk/~earlgb/Publications/Vam%20Driessche%20et%20al%20New%20Perspectives%20on%20Mineral%20Nucleation%20and%20Growth%20Springer%202016_Chapter12.pdf):

"Induction time measurements performed by Liu and Nancollas (1973) suggested that the nucleation of gypsum is associated with an appreciable activation barrier, involving a critical nucleus composed of approximately six ions, as predicted based on a “nonclassical nucleation model” introduced by Christiansen and Nielsen (1952)."

The formed CuCl2 can be further purified by concentrating the solution and cooling to collect CuCl2.2H2O.

I would guess you can directly mix copper sulfate solution with concentrated $\ce{HCl}$ to yield dissolved $\ce{CuCl2}$ and $\ce{H2SO4}$. This is of course in competition with (re-)formation of $\ce{CuSO4}$ but I would be interested in seeing how excess $\ce{HCl}$ would affect yield.

Also -- I made $\ce{CuCl2}$ by dissolving copper metal in concentrated $\ce{HCl}$, adding concentrated $\ce{H2O2}$ (slowly) and then evaporating off the water solvent. The dehydrated form is a brown powder and moderately irratiting. Easily soluble in water and has a blue/green solution color. -- So some method of reducing the copper sulfate to copper-metal (e.g. electrolysis), and then this dissolution in $\ce{HCl/H2O2}$ should do it.

Acid fumes deem a fume hood necessary, but decomposition of $\ce{H2O2}$ just gives off water and oxygen gas.

Along the lines of your precipitating idea, using barium chloride or lead chloride to form the corresponding insoluble sulfate would potentially be a faster, one step process, although perhaps more expensive. After, you decant the remaining $\ce{CuCl2}$ and evaporate solvent.

• Adding conc. $\ce{HCl}$ to $\ce{CuSO4}$ solution will give a yellow solution containing $\ce{[CuCl4]^{2-}}$ ions. It definitely won't produce $\ce{CuCl2}$ as all the ions will stay in solution. – bon Jul 31 '15 at 15:08
• I thought it may form a more complex ion, thanks. By the way --how does one write subscripts without italicizing (with LaTex)? I'd like to contribute here more often. @bon – khaverim Jul 31 '15 at 15:13
• @bon Nevermind, I can see it from your edits, ty – khaverim Jul 31 '15 at 15:15
• See here for information on formatting. – bon Jul 31 '15 at 15:20

Displacement reaction of copper by sodium will work well if ethanol is used to precipitate the sodium sulfate. Copper chloride is soluble in ethanol (>50 g/100 mL) while sodium sulfate is not. A mixture of concentrated salts in water, followed by dilution with fair amounts of ethanol will allow recovery of high-purity copper chloride dihydrate after proper washing and drying. However, you must check for ethanol contamination in the crystals.